Bionics is a discipline focusing on the application of advanced technologies to biological systems. Generally speaking, a bionic is a manufactured device or engineered tissue that substitutes for, or augments, the function of a natural limb, organ or other portion of a biological body. Although commonly thought of within the context of science fiction, significant strides have been made in the field of bionics. Research in bionics offers the possibility of restoring function to impaired and damaged biological systems.
One significant application of bionics is in the area of vision. Over 30 million people have been subject to retinal degenerative diseases. Retinal degenerative diseases can generally be broken into two categories: Retinitis Pigmentosa (RP) and Age-related Macular Degeneration (AMD).
Retinitis Pigmentosa (RP) is a general term for a number of diseases that predominately affect the photoreceptor layer cells of the retina. The injured photoreceptor cell layer reduces the retina's ability to sense light. Most cases of RP affect the mid-peripheral vision first, which sometimes progresses to affect the far-periphery and the central areas of vision. This narrowing of the field of vision (aka “tunnel vision”) can sometimes result in complete blindness.
Age-Related Macular Degeneration (AMD) refers to a degenerative condition that occurs most frequently in the elderly, where decreased function is observed in specific cellular layers of the retina's macula. The outer retina and inner retina photoreceptor layer are affected such that patients experience a loss of their central vision, which affects their ability to read and perform visually demanding tasks.
Significant research has been conducted in the areas of artificial vision to develop an artificial silicon retina (ASR). An ASR is a micro-electronic circuit (or microchip) that is implantable in the body and arranged to stimulate damaged retinal cells, allowing the patient to send visual signals to the brain. An ASR contains thousands of light sensitive cells that convert the light into a series of electrical pulses that mimic the functions of the cones and rods in the eye. Clinical trials have been conducted for ASR devices, although currently vision quality is relatively poor. Additional research in ASR-type devices continues to progress and the promise of restored vision, even to the blind, may be within our grasp.
Another significant application of bionics is in the area of hearing. Hearing loss may be either congenital (acquired either genetically or in utero) or acquired. Various types of hearing loss include: conductive hearing loss, sensorineural hearing loss, or neural hearing loss.
Conductive hearing loss is caused by a problem in the outer or middle ear, wherein the sound path is blocked impairing the ability of the eardrum and bones from vibrating. Conductive losses are usually mild or moderate in nature and in some cases a conductive hearing loss can be temporary. In most cases of conductive hearing loss, hearing can be either restored through surgery and/or medication, or improved with hearing aids.
Sensorineural hearing loss is caused by a problem in the inner ear or cochlea. A damaged inner ear does not change sound waves into the tiny electrical pulses that the auditory nerves need to send sound information to the brain. Sensorineural hearing losses are usually permanent, and cannot typically be repaired through surgical procedures. Conventional hearing aids can usually help in mild to severe hearing loss.
Neural hearing loss is due to a problem in the nerve pathway, wherein the auditory nerve is damaged or missing such that signals cannot be sent to the brain. In very rare cases, hearing loss is caused by the absence of or damage to the auditory nerve, resulting in a neural hearing loss. Conventional hearing aids are of little benefit because to a neural hearing loss since the nerve is unable to pass on information to the brain.
Cochlear implants can be a very effective option for those with severe, profound hearing loss who obtain little or no benefit from conventional acoustic amplification such as hearing aids. However, cochlear implants will not help unless there is some auditory nerve function. A cochlear implant is an electronic device that consists of two main parts: an internal implanted part called the implant, and an external part known as the speech processor. Sounds are picked up by a microphone and turned into an electrical signal. This signal goes to the speech processor where it is “coded” (turned into a special pattern of electrical pulses). The coded electrical pulses are sent to the coil and are then transmitted across the intact skin (by radio waves) to the implant. The implant sends a pattern of electrical pulses to the electrodes in the cochlea. The auditory nerve picks up these tiny electrical pulses and sends them to the brain. The brain recognizes these signals as sound.
The examples described above illustrate but a few applications for bionics. While bionics cannot cure many of the ailments that exist, current developments present a number of opportunities for improving quality of life. Exciting new research in the field of bionics continues in such areas as drug delivery systems for chronic disabilities, neuromuscular stimulation devices that enable the activation or enhancement of motion to replace lost or impaired motor control, micro-stimulators to treat chronic disorders of the central nervous system, as well as many others.